Tower of Augery

This trap is for all those adventurers that think they can just march up to whatever they want with no consequences.

The victims… err, adventurers come across an underground tower in a cavern that is rumored to contain the vast wealth and treasure of a wizard or lich. The tower has a single entrance at ground level, a solid iron portal or some such. It should be mildly challenging to gain entry, perhaps even trapped. Once they get inside, they see a hollow, windowless tower, with a spiral staircase curving its way around the inside walls and stretching up to the top of the tower, which is just out of sight.

Once the characters start climbing the stairs, it activates the trap. The stairs cause the top and bottom of the tower to silently raise and lower. The bottom augers its way into the ground, and the top drills into the cavern ceiling. The entire inside of the tower, including the floor, move. Each step the characters take drills the floor further into the ground and the top of the tower further into the ceiling. After several steps, the entrance at the bottom of the tower will be hopelessly buried under the earth. The cavern itself is underneath a large subterranean lake. At some point, the top of the tower will drill into the bottom of the lake, filling the tower with thousands of gallons of water, unless the lake was made of lava or acid, that is.

The only way out of the tower, once the entrance is buried is to use a mode of travel that does not use the stairs to reach a higher-than-ground-level height. At this point, the wall of the tower itself must be breached to escape. You can make this easier/harder by varying the thickness and materials of the wall.

Interaction

PFRPG:

D&D 4e:

Detecting

To detect the drilling motion

Very Hard Perception (bonus for dwarves)

As for PFRPG

To detect the fact that the ceiling is getting further away

Very Hard Perception to Easy Perception as more steps are taken

As for PFRPG

To detect the imminent collapse of the ceiling

Hard Perception (bonus for dwarves)

As for PFRPG

Effects

Ceiling Collapse

This dumps thousands of gallons of liquid into the tower. If it is water, the characters will take a high amount of damage, something like 10d10 Reflex based damage. Afterwards, std drowning rules apply. Other, more dangerous liquids (lava, acid, etc) are pretty much going to add more damage, and be instant death unless precautions have been taken.